1. Field of the Invention
The present invention relates to a lamp energization control circuit and more particularly pertains to a control circuit for controlling the energization of a lamp which is adapted to illuminate images, such as of a date of photography, for imprinting them on a film upon photography.
2. Description of the Prior Art
Cameras are well known which contain therein or have detachably attached thereto a data imprinting device for imprinting on a film images representing data such as the date of photography and the exposure conditions for the photography. Such data imprinting devices ordinarily include a lamp for illuminating the images so that light bearing the images is projected onto the film. To effect the data imprinting in response to a camera exposure operation, the flash synchro switch or flash trigger switch, which is provided in the camera and is actuated in relation with a shutter opening, can be utilized for initiating the energization of the lamp. Further to ensure a proper exposure upon the imprinting, the duration of the lamp energization must be controlled. A typical duration control device is an RC delay circuit including a series or parallel connected resistor and capacitor. In the conventional data imprinting devices, the capacitor of the RC delay circuit had to be short-circuited or charged. Accordingly electric energy was consumed for that purpose.
Further, when the flash synchro switch is used for the initiation of the lamp energization, it is likely to occur that an extremely high voltage from the electronic flash device mounted on the camera and electrically connected to the flash synchro switch through a direct contact terminal, is applied to the data imprinting device via the flash synchro terminal for the synchro cord.